What was the first instant messenger?

ICQ was the first stand-alone instant messenger (IM) originally developed by the Israeli company Mirabilis in 1996. The name ICQ derives from the English phrase "I Seek You". The technology Mirabilis developed for ICQ was distributed free of charge. The technology's success encouraged AOL to acquire Mirabilis on June 8, 1998 . At its peak around 2001, ICQ had more than 100 million accounts registered.